Parasitic draw

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Mr B
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Re: Parasitic draw

Post by Mr B » Wed Feb 17, 2021 9:49 pm

Bug wrote:
Wed Feb 17, 2021 8:19 am
Hold up!
Think there's a misunderstanding occurring here?
Yes, the lenses are held on with small screws and seals which I always thought were to keep the moisture out? Doing them up too tight may indeed crack the lenses.
However, I think the question may be more to do with the two big fat screws that hold the light assembly in place, from inside the boot? If you do these up too tight, it cracks the back plate. As this carries the common earth for all the lights, back through the mounting screws to the bodywork, then a crack can cause all sorts of odd lighting issues. I've even seen it cause a problem with front sidelights! That one took a a while to trace.
Hi Bug,

Yes it's the 2 large screws that hold each rear cluster in place that have had bolts put in them.

Wayne

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Re: Parasitic draw

Post by Bug » Thu Feb 18, 2021 8:38 am

Mr B wrote:
Wed Feb 17, 2021 9:49 pm
Bug wrote:
Wed Feb 17, 2021 8:19 am
Hold up!
Think there's a misunderstanding occurring here?
Yes, the lenses are held on with small screws and seals which I always thought were to keep the moisture out? Doing them up too tight may indeed crack the lenses.
However, I think the question may be more to do with the two big fat screws that hold the light assembly in place, from inside the boot? If you do these up too tight, it cracks the back plate. As this carries the common earth for all the lights, back through the mounting screws to the bodywork, then a crack can cause all sorts of odd lighting issues. I've even seen it cause a problem with front sidelights! That one took a a while to trace.
Hi Bug,

Yes it's the 2 large screws that hold each rear cluster in place that have had bolts put in them.

Wayne
In that case, sorry I don't have photos, but if you take them off it is easy to see how the screws (bolts in your case) can pull the fitting too tight, usually resulting in cracks either side of the threaded screw holes. The light units earth through these screws, so make sure all is intact and that the fittings are all clean.
Basically, do them up finger tight, then slowly add a turn to each screw, while trying to move the unit by hand. As soon as they won't move, stop turning.

Mr B
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Re: Parasitic draw

Post by Mr B » Sun Feb 28, 2021 12:06 am

Bug wrote:
Thu Feb 18, 2021 8:38 am
Mr B wrote:
Wed Feb 17, 2021 9:49 pm
Bug wrote:
Wed Feb 17, 2021 8:19 am
Hold up!
Think there's a misunderstanding occurring here?
Yes, the lenses are held on with small screws and seals which I always thought were to keep the moisture out? Doing them up too tight may indeed crack the lenses.
However, I think the question may be more to do with the two big fat screws that hold the light assembly in place, from inside the boot? If you do these up too tight, it cracks the back plate. As this carries the common earth for all the lights, back through the mounting screws to the bodywork, then a crack can cause all sorts of odd lighting issues. I've even seen it cause a problem with front sidelights! That one took a a while to trace.
Hi Bug,

Yes it's the 2 large screws that hold each rear cluster in place that have had bolts put in them.

Wayne
In that case, sorry I don't have photos, but if you take them off it is easy to see how the screws (bolts in your case) can pull the fitting too tight, usually resulting in cracks either side of the threaded screw holes. The light units earth through these screws, so make sure all is intact and that the fittings are all clean.
Basically, do them up finger tight, then slowly add a turn to each screw, while trying to move the unit by hand. As soon as they won't move, stop turning.
Hey Bug,

You was right, the damage is easy to see - off side cluster is toast, someone got a bit over excited when doing up the fixing bolts, also discovered that someone had cut the wire to the number plate lights and instead spliced into the rear side light circuit to get power to them, the actual number plate feed wire was still live and working so god knows why they did that!

The Joy's of old cars eh?

Thanks for your help mate

Wayne

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Re: Parasitic draw

Post by Bug » Mon Mar 01, 2021 8:46 am

No worries.
Glad it helped, and more importantly it was nice to get feedback. ;)

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Major_Tom
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Re: Parasitic draw

Post by Major_Tom » Tue Mar 02, 2021 1:19 am

Bug wrote:
Wed Feb 17, 2021 8:19 am
Hold up!
Think there's a misunderstanding occurring here?
Yes, the lenses are held on with small screws and seals which I always thought were to keep the moisture out? Doing them up too tight may indeed crack the lenses.
However, I think the question may be more to do with the two big fat screws that hold the light assembly in place, from inside the boot? If you do these up too tight, it cracks the back plate. As this carries the common earth for all the lights, back through the mounting screws to the bodywork, then a crack can cause all sorts of odd lighting issues. I've even seen it cause a problem with front sidelights! That one took a a while to trace.
That's interesting - one of my sidelights comes on when I brake.
I'm the one that leaves all those shoes in the carriageway.

Bug
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Re: Parasitic draw

Post by Bug » Tue Mar 02, 2021 8:21 am

Major_Tom wrote:
Tue Mar 02, 2021 1:19 am
Bug wrote:
Wed Feb 17, 2021 8:19 am
Hold up!
Think there's a misunderstanding occurring here?
Yes, the lenses are held on with small screws and seals which I always thought were to keep the moisture out? Doing them up too tight may indeed crack the lenses.
However, I think the question may be more to do with the two big fat screws that hold the light assembly in place, from inside the boot? If you do these up too tight, it cracks the back plate. As this carries the common earth for all the lights, back through the mounting screws to the bodywork, then a crack can cause all sorts of odd lighting issues. I've even seen it cause a problem with front sidelights! That one took a a while to trace.
That's interesting - one of my sidelights comes on when I brake.
I don't believe you Tom! When did you ever brake? :D

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Re: Parasitic draw

Post by Mc Tool » Tue Mar 02, 2021 7:21 pm

When I got my crapi I couldnt find the wires on tother end of fog light switch ,we have fog lights on the front here so thats the end I went for , and then there was confusion at the rear because I had spare wires and wires to xtra brake lights. Somebody has disconnected the rear fogs and hooked them up to the brake lights so I got 4 brake lights (Mavis🤬 Cleaver still managed to run up the arse of me) , and a spare switch on the dash which is now for the fuel pump .......,the idea being that if someone half inches crapi , not knowing about the switch, the car will run for a bit then crap out ,and most car thieves wont hang about in a stolen motor thats blocking traffic and legs it .......I get my car back
Id rather have a bottle in front of me :beer: than a frontal lobotomy 🤯

Mr B
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Re: Parasitic draw

Post by Mr B » Sun Mar 07, 2021 11:13 am

Morning all,

So I replaced the offside rear light cluster as it was suffering from the cracking that Bug mentioned, however as a result of replacing it that "its always had it dimly glowing ignition light" is now much worse than what it was which I cannot understand as the donor cluster is in perfect condition, before I put it on the car I cleaned up all the connections and it is working perfectly I.e. all the lights are doing what they should be.

Any thoughts guys?

Wayne

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stevemarl
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Re: Parasitic draw

Post by stevemarl » Sun Mar 07, 2021 11:31 am

It`s probably nothing to worry about. It`s a 40 year old car with 40 year old wiring. There will be numerous joins, connnectors, terminals, between the Alt, battery, ignition light, each of which will have deteriorated slightly and introduced tiny resistance/ voltage drops into the system: as long as the light glows brightly when engine off and decreases significantly when on , and the alternator has correct output, it`s not a cause for concern. (Also he more electrics you have on, the brighter it will glow, this is normal. Maybe now your back lights are working...?)

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